This invention relates to an improved process for the production of certain dichloroacetamides. More particularly, it relates to an improved process for the production of N,N-diallyldichloroacetamide and N-dichloroacetyl oxazolidines having the formula ##STR3## in which R is hydrogen or C.sub.1 -C.sub.3 alkyl. The amide or oxazolidine is prepared by reaction of dichloroacetyl chloride with, respectively N,N-diallylamine or an oxazolidine having the formula ##STR4## in which R is similarly hydrogen or C.sub.1 -C.sub.3 alkyl, in the presence of an aqueous solution of sodium hydroxide.
In conducting such reactions, certain techniques have been found to be satisfactory in general in reducing the production of byproducts, particularly byproducts formed by reaction of the dichloroacetyl chloride with intermediates formed during the reaction step or the production of undesirable quantities of amine salts.
U.S. Pat. No. 3,914,302 of Jimmy Chan, et al. describes a process for the production of N,N-diallyldichloroacetamide in yields above 80% having essentially no amine salt or dichloroacetic acid as byproduct, by reaction of dichloroacetyl chloride with N,N-diallylamine in a batch process with the use of a sufficient amount of an aqueous sodium hydroxide solution having a concentration of preferably 15-50% and most preferably about 17-20%, such that at all times during the reaction, the pH of the reaction mixture remains at a value greater than 10, preferably at a value from 11 to 13. The process involves violent agitation of a mixture of the amine and aqueous sodium hydroxide, the dichloroacetyl chloride being slowly added. At the same time the temperature of the reaction mixture is maintained from about -10.degree. to 100.degree. C., more preferably from about 20.degree. to about 50.degree. C. The most preferred temperature is about 30.degree. C.
In that process the molar ratio of dichloroacetyl chloride to diallylamine is also important and should be from about 0.7:1 to about 0.95:1. The desired amide is recovered by separation of the aqueous and organic phases, followed by stripping the organic phase to remove water and excess amine, and is said to be recovered at a rate of greater than 80% of the theoretical yield based either on diallylamine or dichloroacetyl chloride.
In U.S. Pat. No. 4,038,284 of Harold M. Pitt, there is described a process, carried out on the laboratory scale, for the production of N-substituted oxazolidines of the type mentioned above, and others. The process consists of reacting the oxazolidine with an acid chloride, for example dichloroacetyl chloride, in the presence of a hydrogen chloride acceptor and water. The preferred hydrogen chloride acceptor is sodium hydroxide, in the form of an aqueous solution containing 5 to 50%, preferably about 20%, sodium hydroxide. Reaction temperatures can range from about -5.degree. to about +25.degree. C. The examples illustrate that a yield of 82% of theoretical could be obtained by carrying out the process. However, such a yield required the use of a 33% sodium hydroxide solution which resulted in precipitation of solid sodium chloride.
In the production of N,N-diallylacetamide or the oxazolidine by the batch processes described in these patents, however, there can still result the formation of a substantial amount of sodium dichloroacetate by the side reaction of sodium hydroxide and dichloroacetyl chloride. This results from the contact between the sodium hydroxide solution and the dichloroacetyl chloride, which contact is increased if violent agitation is utilized, as in the process of U.S. Pat. No. 3,914,302.
N,N-diallyldichloroacetamide and the N-dichloroacetyl oxazolidines referred to are useful as herbicidal antidotes in compositions containing certain types of herbicides. An antidote is a compound which when used with a herbicide, enhances the selectivity of a herbicide towards crops, resulting in comparatively less damage or injury to a crop than when the herbicide is employed alone. The herbicide continues to function as a herbicide towards weed species.
More specifically, these compounds are useful as antidotes in combination with thiocarbamate and acetanilide herbicides.
Thiocarbamate herbicides have the formula ##STR5## in which: R.sub.1 is C.sub.1 -C.sub.6 alkyl or C.sub.2 -C.sub.6 alkenyl;
R.sub.2 is C.sub.1 -C.sub.6 alkyl, C.sub.2 -C.sub.6 alkenyl, cyclohexyl or phenyl; or PA1 R.sub.1 and R.sub.2 together with the nitrogen atom form a heterocyclic ring; and PA1 R.sub.3 is C.sub.1 -C.sub.6 alkyl, C.sub.1 -C.sub.4 haloalkyl; C.sub.5 -C.sub.10 cycloalkyl; phenyl; substituted phenyl, in which the substituents are C.sub.1 -C.sub.4 alkyl; C.sub.1 -C.sub.4 haloalkyl or halo; benzyl, and substituted benzyl, in which the substituents are C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 haloalkyl or halo. PA1 R.sub.4 is C.sub.1 -C.sub.6 alkyl, C.sub.2 -C.sub.10 alkoxyalkyl, C.sub.3 -C.sub.6 alkoxy-carbonylalkyl and dioxolan, and PA1 R.sub.5 is chlorine, bromine or iodine. PA1 "halo" includes fluoro, chloro, bromo and iodo; PA1 "alkyl", "alkenyl", "haloalkyl" and "alkoxyalkyl" include both straight and branched chain moieties; and PA1 "haloalkyl" includes both mono- and poly-halogenated moieties. PA1 (a) N,N-diallyldichloroacetamide; and PA1 (b) N-dichloroacetyl oxazolidines having the formula ##STR7## in which R is hydrogen or C.sub.1 -C.sub.3 alkyl, by the reaction of dichloroacetyl chloride with, respectively, N,N-diallylamine or an oxazolidine having the formula ##STR8## in which R is hydrogen or C.sub.1 -C.sub.3 alkyl, in the presence of an aqueous solution of sodium hydroxide, comprising the steps of: PA1 (a) continuously mixing the dichloroacetyl chloride, aqueous solution of sodium hydroxide and either the N,N-diallylamine or the oxazolidine by continuously introducing these substances into a circulating liquid medium to form a reaction mixture; PA1 (b) continuously introducing the reaction mixture into a non-agitated reactor; PA1 (c) retaining the reaction mixture in the reactor for a sufficient time for separation of the reaction mixture into an aqueous phase comprising an aqueous brine and an organic phase comprising the crude, desired product to occur; PA1 (d) continuously withdrawing the aqueous phase from the reactor; PA1 (e) continuously withdrawing one portion of the organic phase containing the crude product from the reactor; PA1 (f) recovering the desired product from the portion of the organic phase withdrawn in step (e); and PA1 (g) continuously withdrawing a second portion of the organic phase from the reactor and continuously recycling it to step (a) to serve as the circulating liquid medium therein.
Examples of thiocarbamate herbicides are: S-ethyldipropyl thiocarbamate, S-ethyl diisobutyl thiocarbamate, S-propyl dipropyl thiocarbamate, S-2,3,3-trichlorallyl diisopropyl thiocarbamate; S-ethyl cyclohexylethyl thiocarbamate and S-ethyl hexahydro-1H-azepine-1-carbathioate.
Acetanilide herbicides have the formula ##STR6## in which: X, Y and Z are independently hydrogen or C.sub.1 -C.sub.4 alkyl;
Examples of acetanilide herbicides are: 2-chloro-2',6'-diethyl-N-(methoxymethyl)acetanilide; 2-chloro-2-methyl, 6'-ethyl-N-[methoxypropyl-(2)]acetanilide; 2-chloro-2',6'-dimethyl-N-(methoxyethyl)acetanilide; 2-chloro-2'-methyl, 6'-ethyl-N-(ethoxymethyl)acetanilide; 2-chloro-N-isopropyl acetanilide; 2-chloro-2',6'-diethyl-N-(n-butoxymethyl) acetanilide; and 2-chloro-N-carbethoxymethyl-2',6'-diethyl acetanilide.
As used above:
Such compositions contain, in general, a herbicidally effective amount of the thiocarbamate or acetanilide herbicide and an antidotally effective amount of the N,N-diallyldichloroacetamide or N-dichloroacetyl oxazolidine.